#######################################################################
#                     Application Information                          #
########################################################################  

# Application Name: Web Store
# Application Authors: Eric Tachibana (Selena Sol) and Gunther Birznieks
# Version: 2.0
# Last Modified: 17NOV98
#     
# Copyright:
#     
#     You may use this code according to the terms specified in
#     the "Artistic License" included with this distribution.  The license
#     can be found in the "Documentation" subdirectory as a file named
#     README.LICENSE. If for some reason the license is not included, you
#     may also find it at www.extropia.com.
#    
#     Though you are not obligated to do so, please let us know if you
#     have successfully installed this application.  Not only do we
#     appreciate seeing the wonderful things you've done with it, but we
#     will then be able to contact you in the case of bug reports or
#     security announcements.  To register yourself, simply send an
#     email to register@extropia.com.
#
#    Finally, if you have done some cool modifications to the scripts, 
#    please consider submitting your code back to the public domain and 
#    getting some community recognition by submitting your modifications  
#    to the Extropia Cool Hacks page.  To do so, send email to
#    hacks@extropia.com
# 
# Basic Usage:
#     
#    1. Read the README.CHANGES, README.LICENSE, and README.SECURITY
#       files and follow any directions contained there
#    
#    2. Change the first line of each of the scripts so that they
#       reference your local copy of the Perl interpreter. (ie:
#       #!/usr/local/bin/perl) (Make sure that you are using Perl 5.0 or
#       higher.)
#     
#    3. Set the read, write and access permissions for files in the
#       application according to the instructions in the
#       README.INSTALLATION file.
#    
#    4. Define the global variables in the setup file you choose according  
#       to the instructions in the README.INSTALLATION file.  Also
#       set the name of the setup file in web_store.cgi if you are not
#       using the default.
#    
#    5. Point your web browser at the script
#       (ie:http://www.yourdomain.com/cgi-bin/web-store.cgi)
# 
# More Information
#    
#    
#    You will find more information in the Documentation sub-directory.
#    We recommend opening the index.html file with your web browser to
#    get a listing of supporting documentation files.

########################################################################
#                     Application Code                                 #
########################################################################

.... stuff deleted here ....

#######################################################################
#                            get_file_lock                            #
#######################################################################

		# get_file_lock is a subroutine used to create a lockfile.
		# Lockfiles are used to make sure that no more than one
		# instance of the script can modify a file at one time.  A
		# lock file is vital to the integrity of your data.
		# Imagine what would happen if two or three people
		# were using the same script to modify a shared file (like
		# the error log) and each accessed the file at the same
		# time.  At best, the data entered by some of the users
		# would be lost.  Worse, the conflicting demands could
		# possibly result in the corruption of the file.
		#
		# Thus, it is crucial to provide a way to monitor and
		# control access to the file.  This is the goal of the
		# lock file routines.  When an instance of this script
		# tries to  access a shared file, it must first check for
		# the existence of a lock file by using the file lock
		# checks in get_file_lock.
		#
		# If get_file_lock determines that there is an existing
		# lock file, it instructs the instance that called it to
		# wait until the lock file disappears.  The script then
		# waits and checks back after some time interval.  If the
		# lock file still remains, it continues to wait until some 
		# point at which the admin has given it permissions to just
		# overwrite the file because some other error must have
		# occurred.
		#
		# If, on the other hand, the lock file has disappeared,
		# the script asks get_file_lock to create a new lock file
		# and then goes ahead and edits the file.
		#
		# The subroutine takes one argument, the name to use for
		# the lock file and is called with the following syntax:
		#
		# &get_file_lock("file.name");

sub get_file_lock 
  {
  local ($lock_file) = @_;
  local ($endtime);
  $endtime = 20;
  $endtime = time + $endtime;

		# We set endtime to wait 20 seconds.  If the lockfile has
		# not been removed by then, there must be some other
		# problem with the file system.  Perhaps an instance of
		# the script crashed and never could delete the lock file.
    
  while (-e $lock_file && time < $endtime) 
    {
    sleep(1);
    }

  open(LOCK_FILE, ">$lock_file") || &CgiDie ("I could not open the lock
				     file");

		# Note: If flock is available on your system, feel free to
		# use it.  flock is an even safer method of locking your
		# file because it locks it at the system level.  The above
		# routine is "pretty good" and it will server for most
		# systems.  But if you are lucky enough to have a server 
		# with flock routines built in, go ahead and uncomment
		# the next line and comment the one above.

# flock(LOCK_FILE, 2); # 2 exclusively locks the file

  } 

#######################################################################
#                            release_file_lock                        #
#######################################################################

		# release_file_lock is the partner of get_file_lock.  When
		# an instance of this script is done using the file it
		# needs to manipulate, it calls release_file_lock to
		# delete the lock file that it put in place so that other
		# instances of the script can get to the shared file.  It
		# takes one argument, the name of the lock file, and is
		# called with the following syntax:
		#
                # &release_file_lock("file.name");
    
sub release_file_lock 
  {
  local ($lock_file) = @_;
    
# flock(LOCK_FILE, 8); # 8 unlocks the file

		# As we mentioned in the discussion of get_file_lock,
		# flock is a superior file locking system.  If your system
		# has it, go ahead and use it instead of the hand rolled
		# version here.  Uncomment the above line and comment the
		# two that follow.

  close(LOCK_FILE);
  unlink($lock_file);
  }